Blown oil seal

My Chevy Cavalier Z24 2.4 liter has been running rough since I flooded it in a flash flood about a month ago. I got the water out and got it running again, but the last few days it has been idling rough and this morning I heard an explosion and it lost all of its oil. It still starts and runs very rough, but any oil I put in goes straight on the ground. I'm not sure what caused the explosion but I am trying to figure out what exactly blew and how bad it will be to fix.